Naoaki Yokoyama

Naoaki Yokoyama


Research Focus & Metrics

Academic Career Length

29Years (1998-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 October 2014 in Infection, Genetics and Evolution
Verified
Journal Article
Closed access
TSThillaiampalam Sivakumar
Thillaiampalam Sivakumar
KHKyoko Hayashida
Kyoko Hayashida
CSChihiro Sugimoto
Chihiro Sugimoto
NYNaoaki Yokoyama
Naoaki Yokoyama

ThankGod OnyicheThankGod Onyiche
ThankGod Onyiche
SKSUGANUMA Keisuke
SUGANUMA Keisuke
Ikuo IgarashiIkuo Igarashi
Ikuo Igarashi
NYNaoaki Yokoyama
Naoaki Yokoyama
Xuenan XuanXuenan Xuan
Xuenan Xuan
OTOriel Thekisoe
Oriel Thekisoe
Equine Piroplasmosis (EP) is a tick-borne disease caused by apicomplexan protozoan parasites, Babesia caballi and Theileria equi. The disease is responsible for serious economic losses to the equine industry. It principally affects donkeys, horses, mules, and zebra but DNA of the parasites has also been detected in dogs and camels raising doubt about their host specificity. The disease is endemic in tropical and temperate regions of the world where the competent tick vectors are prevalent. Infected equids remain carrier for life with T. equi infection, whilst, infection with B. caballi is cleared within a few years. This review focuses on all aspects of the disease from the historical overview, biology of the parasite, epidemiology of the disease (specifically highlighting other non-equine hosts, such as dogs and camels), vector, clinical manifestations, risk factors, immunology, genetic diversity, diagnosis, treatment, and prevention.

1 February 2015 in Parasitology International
Verified
Journal Article
Closed access
AEAhmed Elsify
Ahmed Elsify
TSThillaiampalam Sivakumar
Thillaiampalam Sivakumar
Mohamed NayelMohamed Nayel
Mohamed Nayel
ASAkram Salama
Akram Salama
AEAhmed Elkhtam
Ahmed Elkhtam
NYNaoaki Yokoyama
Naoaki Yokoyama

1 June 2009 in Clinical and Vaccine Immunology
Verified
Journal Article
Closed access
YNYoshifumi Nishikawa
Yoshifumi Nishikawa
HZHoushuang Zhang
Houshuang Zhang
YIYuzuru Ikehara
Yuzuru Ikehara
NKNaoya Kojima
Naoya Kojima
XXXuenan Xuan
Xuenan Xuan
NYNaoaki Yokoyama
Naoaki Yokoyama
The present study demonstrates that the subcutaneous administration ofNeospora caninumdense granule protein 7 (NcGRA7) entrapped in liposomes coated with mannotriose strongly induces the parasite-specific T-helper type 1 immune response and humoral antibody in mice. Although anti-NcGRA7 immunoglobulin G1 antibody production was induced in mice injected with NcGRA7 alone, the dams and offspring were never protected fromN. caninuminfection. The immunization of mice with liposome-entrapped NcGRA7 before pregnancy resulted in increased offspring survival and decreased the infection rates in the brains of dams after parasite infection at 6 to 9 days of gestation. In conclusion, oligomannose-coated liposome-entrapped NcGRA7 can be used as a new type of effective vaccine to control neosporosis.

1 December 2012 in Infection, Genetics and Evolution
Verified
Journal Article
Closed access
NYNaoaki Yokoyama
Naoaki Yokoyama
TSThillaiampalam Sivakumar
Thillaiampalam Sivakumar
NONaomi Ota
Naomi Ota
IIIkuo Igarashi
Ikuo Igarashi
YNYukio Nakamura
Yukio Nakamura
HIHisashi Inokuma
Hisashi Inokuma

28 May 2019 in Parasites & Vectors
Verified
Journal Article
Open access
PDF file
ABAmany Magdy Beshbishy
Amany Magdy Beshbishy
Gaber El-Saber BatihaGaber El-Saber Batiha
Gaber El-Saber Batiha
NYNaoaki Yokoyama
Naoaki Yokoyama
Ikuo IgarashiIkuo Igarashi
Ikuo Igarashi
There are no effective vaccines against Babesia and Theileria parasites; therefore, therapy depends heavily on antiprotozoal drugs. Treatment options for piroplasmosis are limited; thus, the need for new antiprotozoal agents is becoming increasingly urgent. Ellagic acid (EA) is a polyphenol found in various plant products and has antioxidant, antibacterial and effective antimalarial activity in vitro and in vivo without toxicity. The present study documents the efficacy of EA and EA-loaded nanoparticles (EA-NPs) on the growth of Babesia and Theileria. In this study, the inhibitory effect of EA, β-cyclodextrin ellagic acid (β-CD EA) and antisolvent precipitation with a syringe pump prepared ellagic acid (APSP EA) was evaluated on four Babesia species and Theileria equi in vitro, and on the multiplication of B. microti in mice. The cytotoxicity assay was tested on Madin-Darby bovine kidney (MDBK), mouse embryonic fibroblast (NIH/3T3) and human foreskin fibroblast (HFF) cell lines. The half-maximal inhibitory concentration (IC50) values of EA and β-CD EA on B. bovis, B. bigemina, B. divergens, B. caballi and T. equi were 9.58 ± 1.47, 7.87 ± 5.8, 5.41 ± 2.8, 3.29 ± 0.42 and 7.46 ± 0.6 µM and 8.8 ± 0.53, 18.9 ± 0.025, 11 ± 0.37, 4.4 ± 0.6 and 9.1 ± 1.72 µM, respectively. The IC50 values of APSP EA on B. bovis, B. bigemina, B. divergens, B. caballi and T. equi were 4.2 ± 0.42, 9.6 ± 0.6, 2.6 ± 1.47, 0.92 ± 5.8 and 7.3 ± 0.54 µM, respectively. A toxicity assay showed that EA, β-CD EA and APSP EA affected the viability of cells with a half-maximal effective concentration (EC50) higher than 800 µM. In the experiments on mice, APSP EA at a concentration of 70 mg/kg reduced the peak parasitemia of B. microti by 68.1%. Furthermore, the APSP EA-atovaquone (AQ) combination showed a higher chemotherapeutic effect than that of APSP EA monotherapy. To our knowledge, this is the first study to demonstrate the in vitro and in vivo antibabesial action of EA-NPs and thus supports the use of nanoparticles as an alternative antiparasitic agent.